This proposal is to develop a thromboresistant, heparinized-blood compatible material. A proposed hypothesis will be investigated to test the blood-material surface interactions and compatibility. In improving the thromboresistance of heparinized surfaces, the covalent-bonded heparin should posses enough mobility that gives itself the same molecular shape and size as it does in a freely-soluble state. To test this hypothesis, a conventional covalently-bonded heparinized styrene-butadiene-styrene block copolymer will be synthesized as the control. The proposed material has the same structure as the control except hydrophillic polymer chain is inserted between the polymer surface and the pendent heparin to give the desired mobility. The length of the polymer chain can be precisely controlled by Living Polymerization. Poly(oxyethylene) is chosen as the hydrophillic chain. It not only gives pendent heparin enough mobility, but also acts as a hydrogel reducing the absorption of blood components. The synthetic techniques and evaluation methods are also proposed and described.